Recuperator for use with turbine/turbo-alternator

ABSTRACT

An annular recuperator for use with an annular combustor. The annular recuperator includes a frame and an enclosure provided about its frame that defines a recuperator chamber. A plurality of involute shaped sealed and open recuperators are received in the recuperator chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 09/571,195 filed May 16, 2000 entitled “Recuperator for Use WithTurbine/Turbo-Alternator” herein incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to heat exchangers and, more particularly,to recuperators for use with turbines and turbo-alternators.

2. Description of the Prior Art

Many gas turbine engines use a heat exchanger or recuperator to increasethe operational efficiency of the engine by extracting heat from theexhaust gas of the engine and preheating the intake air before it ispassed to a combustor section of the engine. Typically, a recuperatorfor a gas turbine engine is annular-shaped in cross section andpositioned around the engine. Such “annular” recuperators generallyinclude a core which is commonly constructed of a plurality ofrelatively thin, flat metal sheets having an angled or corrugated spacerfixedly attached therebetween. The sheets are joined into cells andsealed at opposite sides, forming passages between the sheets. The cellsare stacked or rolled and form alternating cold air intake cells and hotair exhaust cells. The hot exhaust air from the engine heats the sheetsand the spacers; and the cold air cells are heated by conduction fromthe sheets and the spacers.

One annular heat exchanger is known from U.S. Pat. No. 5,081,834 toDarragh. The heat exchanger disclosed by the Darragh patent isconfigured to resist the internal forces and pressures and the thermalstresses inherent from the cyclic operation of a gas turbine engine. Thecore of the heat exchanger disclosed by the Darragh patent has aplurality of heat recipient passages which have a uniformcross-sectional area throughout the entire length of the passages. Inaddition, the core has a plurality of heat donor passages which have auniform cross-sectional area throughout the length of the passages. Theheat recipient passages contain a heat recipient fluid during operationand the heat donor passages contain a heat donor fluid during operation.The core includes a plurality of stacked primary cells each defining oneof the passages (heat recipient passages or heat donor passages)therein. The cells are secured together forming a generally annularshaped core in cross section. Each of the plurality of cells has aninvolute curve shape and includes at least a pair of primary surfacepleated sheets.

A major disadvantage with heat exchangers such as that disclosed by theDarragh patent is that the heat recipient passages and the heat donorpassages are defined by a plurality of metal sheets that extend betweenan inner diameter of the heat exchanger and an outer diameter of theheat exchanger. Each of these sheets is a potential leak path betweenthe heat donor fluid and the heat recipient fluid, which will degradethe efficiency of the heat exchanger and the power output of the engine.

Accordingly, an object of the present invention is to provide arecuperator for use with a turbine or a turbo-alternator that reducesthe possibility of leakage between a heat donor fluid and a heatrecipient fluid. It is a further object of the present invention toprovide a relatively inexpensive recuperation for use with a turbine ora turbo-alternator.

SUMMARY OF THE INVENTION

The above objects are accomplished with a cylindrical or annular shapedrecuperator made in accordance with the present invention.

The present invention is a fluid recuperator that includes a frame, anenclosure provided about the frame defining a recuperator chamber, afirst fluid inlet in fluid communication with the recuperator chamber, afirst fluid outlet in fluid communication with the recuperator chamber,a plurality of spaced sealed recuperator units received within therecuperator chamber, each of the recuperating units having a body withan outer surface and an inner surface that defines a second fluid flowchamber, a second fluid inlet in fluid communication with the pluralityof sealed recuperator units and a second fluid outlet in fluidcommunication with said plurality of sealed recuperator units. Therecuperator is adapted to have a first fluid flow through the first gasinlet, the recuperator chamber across the sealed recuperator units outersurface and through the first fluid outlet, respectively, while a secondfluid passes through the second fluid inlet, through the second fluidflow chambers, contacting inner surfaces of the sealed recuperator unitsand through said second fluid outlet in a manner that the first fluidand the second fluid do not mix while passing through the recuperatorchamber and heat transfer takes place between the fluids through thebodies of the sealed recuperator units.

The present invention is also a method for manufacturing a sealedrecuperator unit, that includes the steps of:

(a) providing a first section having an embossment;

(b) providing a second section;

(c) placing a corrugated member in the embossment;

(d) placing the second section over the first section; and

(e) welding said first section to said second section thereby forming asealed recuperator unit.

The present invention is also a method for cleaning the above describedrecuperator, that includes the steps of:

(a) removing at least one of said open recuperator units which isfouled; and

(b) replacing the removed open recuperator unit with a cleanedrecuperator unit.

The present invention is also a method for forming a joint, thatincludes the steps of:

(a) providing a first metallic member having a first thickness andhaving a lip;

(b) providing a second metallic member having a slot for receipt of thelip, the second metallic member having a second thickness, the secondthickness is greater than the first thickness;

(c) placing the lip within the slot so that a tip of the lip extendsbeyond the slot;

(d) heating the tip until the tip melts;

(e) heating the second metallic member adjacent the tip so that themelted tip causes the first metallic member to weld to the secondmetallic member about the lip; and

(f) permitting the first metallic member and the second metallic memberto cool, thereby forming a welded joint about the lip.

Further details and advantages of the present invention will becomeapparent with reference to the following detailed description, inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a recuperator and turbine engine;

FIG. 2 is a sectional view of an upper portion of the recuperator andturbine engine shown in FIG. 1;

FIG. 3 is a perspective view, partially cut away, of the recuperatorshown in FIG. 1;

FIG. 4 is an end view of the recuperator shown in FIG. 1;

FIG. 5 is a partial end view of the recuperator shown in FIG. 4;

FIG. 6 is a partial end view of the recuperator shown in FIG. 4,immediately adjacent an outer shell of the recuperator;

FIG. 7 is a partial end view of the recuperator shown in FIG. 4,immediately adjacent an inner shell of the recuperator;

FIG. 8 is a side view of a turbine section of the turbine engine shownin FIG. 1, with the turbine section having a hot gas bypass;

FIG. 9 is an axial end view of the hot gas bypass shown in FIG. 8;

FIGS. 10 a and 10 b are a sectional view of a recuperator and turbineengine made in accordance with the present invention;

FIG. 11 is a partial perspective sectional view of a portion of therecuperator shown in FIG. 10;

FIG. 12 is a partial top perspective view of another portion of therecuperator shown in FIG. 10;

FIG. 13 is a plan view of a sealed recuperator unit made in accordancewith the present invention;

FIG. 14 is a top perspective exploded view of the sealed recuperatorunit shown in FIG. 10;

FIG. 15 is a front elevational view of the combustor housing;

FIG. 16 is a side elevational view of the combustor housing shown inFIG. 15;

FIG. 17 is an end elevational view of the combustor housing shown inFIG. 15;

FIG. 18 is a section taken along lines 18—18 in FIG. 17;

FIG. 19 is a section taken along lines 19—19 in FIG. 17;

FIG. 20 is a partial sectional view prior to the formation of a joint;and

FIG. 21 is the formation of a joint.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 show a heat exchanger or a recuperator 10 positionedaround a gas turbine engine 12. The engine 12 has been configured tointerface with the annular recuperator 10 and is a typical gas turbineengine that includes a compressor section 14 connected to and in fluidcommunication with the recuperator 10. The recuperator 10 is furtherconnected to and in fluid communication with a combustor 16. Thecombustor 16 is further connected to and in fluid communication with apower turbine 18. The engine 12 defines an air intake 20 for a heatrecipient fluid, such as cold outside air, which is designated by arrows22 in the figures. The power turbine 18 defines a turbine exhaust 24positioned adjacent the combustor 16. A heat donor fluid, such ascombusted hot air, is designated by arrows 26 in the figures and isshown exiting from the turbine 18 in FIGS. 1 and 2. The recuperator 10and the engine 12 are spaced concentrically from a central axisdesignated by reference character L. The recuperator 10 and the engine12 are symmetric about the central axis L. The cold air 22 has a lowertemperature than the hot air 26. The engine 12 generally furtherincludes a first axial end 28 and a second axial end 29.

Referring now to FIGS. 1-3, the recuperator 10 is generally defined byan inner shell 30, an outer shell 32 positioned concentrically aroundthe inner shell 30 and a plurality of end caps 34 attached to a firstend 36 of the inner and outer shells 30, 32 and to a second end 38 ofthe inner and outer shells 30, 32. The inner shell 30 and the outershell 32 generally define an annular shaped recuperator core 40therebetween, wherein heat transfer takes place between the cold air 22and the hot air 26.

The inner shell 30 defines a plurality of cold air inlets or first airinlets 42 at the first end 36 of the inner shell 30. In addition, theinner shell 30 defines a plurality of hot air outlets or first airoutlets 44 at the second end 38 of the inner shell 30. As shown in FIG.3, the first air inlets 42 are spaced at regular intervals around acircumference of the inner shell 30. A similar arrangement for the firstair outlets 44 is provided at the second end 38 of the inner shell 30(not shown). The first air inlets 42 are each in fluid communicationwith an air inlet manifold 46 located within the recuperator core 40.Similarly, each of the first air outlets 44 is in fluid communicationwith an outlet air manifold 48 also located within the recuperator core40. The air inlet manifold 46 is positioned adjacent the first end 36 ofthe inner and outer shells 30, 32. Likewise, the air outlet manifold 48is positioned adjacent the second end 38 of the inner and outer shells30, 32.

The second axial end 29 of the recuperator 10 includes a plurality ofrecuperator inlets 50 that are in fluid communication with the turbineexhaust 24. The recuperator inlets 50 are adapted to channel the hot air26 into the recuperator core 40. Similarly, the first axial end 28 ofthe recuperator 10 includes a plurality of recuperator outlets 52 thatare in fluid communication with a turbine engine exhaust 54. Therecuperator outlets 52 are adapted to channel the hot air 26 from therecuperator core 40 to the engine exhaust 54 where the hot air 26, nowcooled, exits the recuperator 10. As shown in FIGS. 1 and 2, therecuperator 10 generally provides for biaxial flow or counterflow in therecuperation core 40, with the cold air 22 and the hot air 26 flowing inopposite directions in the recuperator core 40.

Referring to FIGS. 3-7, the recuperator 10 further includes a continuousserpentine plate 60 connecting the inner and outer shells 30, 32 andpositioned entirely within the recuperator core 40. The serpentine plate60 preferably fills 360° around the circumference of the inner shell 30.However, in FIGS. 5-7 the serpentine plate 60 is shown filling only aportion of the recuperator core 40. The serpentine plate 60 defines aninvolute contour between the inner and outer shells 30, 32. Theserpentine plate 60, as best shown in FIGS. 5-7, continuously extendsback and forth between an outer surface 62 of the inner shell 30 and aninner surface 64 of the outer shell 32. The serpentine plate 60 ispreferably continuously folded back and forth between the inner andouter shells 30, 32 around an entire circumference of the inner shell 30and defines an involute contour between the inner and outer shells 30,32. The serpentine plate 60 further defines a plurality of alternatingcold air chambers 66 and hot air chambers 68. Each of the cold airchambers 66 and the hot air chambers 68 has an involute shaped crosssection due to the involute contour defined by the serpentine plate 60.The cold air chambers 66 each extend the distance between the air inletmanifold 46 and the air outlet manifold 48 (shown in FIGS. 1 and 2) andare each in fluid communication with the air inlet manifold 46 and theair outlet manifold 48. The end caps 34 are attached to the inner andouter shells 30, 32 so as to define an end wall of each of the cold airchambers 66, as shown in FIG. 3. The cold air chambers 66 are therebyprevented from being in fluid communication with the recuperator inlets50 and the recuperator outlets 52. The end caps 34 isolate the highpressure from the low pressure at the first and second axial ends 28, 29of the recuperator 10.

The hot air chambers 68 extend the length of the recuperator core 40from the first end 36 to the second end 38 of the inner and outer shells30, 32. The hot air chambers 68 are each in fluid communication with oneof the recuperator inlets 50 and one of the recuperator outlets 52 (eachshown in FIGS. 1 and 2). The cold air chambers 66 and the hot airchambers 68 thus preferably extend longitudinally in the recuperatorcore 40 providing the means for the biaxial flow or counterflow in therecuperator core 40.

The cold air chambers 66 each further include a plurality of cold airfins 70 positioned within each of the cold air chambers 66. The cold airfins 70 extend transversely between the serpentine plate 60 definingeach of the cold air chambers 66. The cold air fins 70 are corrugated inthe cold air chambers 66, as is known in the art. The cold air fins 70further divide each of the cold air chambers 66 into a plurality oflongitudinally extending cold air tubes 72. The cold air fins 70 areformed by a continuous sheet 74 that extends between the inner surface64 of the outer shell 32 and the outer surface 62 of the inner shell 30.In a similar manner, the hot air chambers 68 each further include aplurality of hot air fins 76 positioned within each of the hot airchambers 68. The hot air fins 76 extend transversely between theserpentine plate 60 defining each of the hot air chambers 68. The hotair fins 76 are corrugated in the hot air chambers 68, as is known inthe art. The hot air fins 76 further divide each of the hot air chambers68 into a plurality of longitudinally extending hot air tubes 78. Thehot air fins 76 are formed by a continuous sheet 80 that extends betweenthe inner surface 64 of the outer shell 32 and the outer surface 62 ofthe inner shell 30. All contact points between the cold air fins 72, thehot air fins 76, the serpentine plate 60 and the inner and outer shells30, 32 are preferably brazed or welded. Preferably, the inner and outershells 30, 32, the end caps 34, the serpentine plate 60 and thecontinuous sheets 74, 80 forming the respective cold and hot air fins72, 76 are each preferably 0.005 of an inch in thickness. As stated, theserpentine plate 60 preferably fills 360° around the circumference ofthe inner shell 30 and, in addition, only requires one joint between theinner and outer shells 30, 32. In FIGS. 5-7, as stated previously, theserpentine plate 60 is shown filling only a portion of the recuperatorcore 40.

FIGS. 8 and 9 show a hot gas bypass 90 that may be provided at theturbine exhaust 24 to block the hot air 26 from entering the recuperator10 and to direct the hot air 26 directly to the engine exhaust 54. Thehot gas bypass 90 includes a plurality of individual dampers 92 that maybe hydraulically or pneumatically operated between an open position inwhich the hot air 26 is directed to the recuperator 10 and a closedposition in which the hot air 26 is directed to the engine exhaust 54.The hot gas bypass 90 is primarily used when the recuperator 10 is notin use or when it is necessary to control the temperature of the hot air26 exiting the recuperator 10.

Referring again to FIGS. 1-5, operation of the recuperator 10 will nowbe discussed. The cold air 22 enters the engine 12 at the first axialend 28 of the engine 12 through the air intake 20 and flows into thecompressor section 14. The compressor section 14 is in fluidcommunication with the first air inlets 42 to the recuperator 10. Thefirst air inlets 42 channel the cold air 22 into the air inlet manifold46. The cold air 22 flows from the air inlet manifold 46 into each ofthe cold air chambers 66 and, in particular, into each of the cold airtubes 72.

Simultaneously, combusted air, or the hot air 26, from the combustor 16flows through the turbine exhaust 24 and into the recuperator inlets 50.The hot air 26 flows through the recuperator inlets 50 and into each ofthe hot air chambers 68 and, in particular, into each of the hot airtubes 78. The hot air 26 flows through the recuperator core 40 towardthe recuperator outlets 52 through the hot air tubes 78. The cold air 22flows in the opposite direction in the cold air tubes 72 toward the airoutlet manifold 48. Thus, a biaxial or counterflow is present in therecuperator core 40 with the hot air 26 flowing in one direction and thecold air 22 flowing in the opposite direction. It will be apparent tothose skilled in the art that the hot air 26 flows entirely within thehot air chambers 68 and, in particular, the longitudinally extending hotair tubes 78. Similarly, the cold air 22 flows entirely within the coldair chambers 66 and, in particular, the longitudinally extending coldair tubes 72. The serpentine plate 60 forming the cold air chambers 66and the hot air chambers 68 also separates the cold air and hot airchambers 66, 68 and prevents leakage therebetween. Heat transfer occursby conduction and convection between the cold air 22 in the cold airchambers 66 and the hot air 26 in the hot air chambers 68. The presenceof the cold and hot air fins 70, 76 in the respective cold air and hotair chambers 66, 68 increases the thermal efficiency of the heattransfer between the hot air 26 in the hot air chambers 68 and the coldair 22 in the cold air chambers 66, as is well-known in the art.

The cold air 22 preferably enters the air inlet manifold 46 at atemperature of about 440° F. The hot air 26 preferably enters therecuperator inlets 50 at a temperature of approximately 1300° F. Theheat transfer in the recuperator core 40 between the hot air 26 and thecold air 22 preferably results in the cold air 22 having a temperatureof approximately 1175° F. at the air outlet manifold 48 and at the firstair outlets 44. The first air outlets 44, as shown in FIGS. 1 and 2, arein fluid communication with the combustor 16. Thus, the combustor 16receives the cold air 22 at a preheated temperature of about 1175° F.The hot air 26, after the heat transfer takes place in the recuperatorcore 40, preferably exits the engine exhaust 54 at about 575° F.

The inner shell 30, the outer shell 32, the end caps 34, the serpentineplate 60 and the continuous sheets 74, 80 are each preferably made ofmetal and, in particular, any one of the following metals: AISI 347stainless steel or an Inconel® alloy. The hot gas bypass 90 may also bemade of any of the above-listed materials.

FIGS. 10 a-19 show an embodiment of a recuperator 100 made in accordancewith the present invention. Specifically, FIGS. 10 a and 10 b show therecuperator 100 in combination with a gas turbine engine 101 and includean annular combustor 102 similar to that previously described. Theannular combustor 102 is in fluid communication with a turbine 104. Theturbine 104 is in fluid communication with an exhaust passageway 106.The exhaust passageway 106 is in fluid communication with an annularexhaust gas inlet area 108 at one end of the recuperator 100. An exhaustgas outlet plane 110 is defined on an opposite end of the recuperator100. The exhaust gas outlet 110 is in fluid communication with an exit112. The general arrangement of this embodiment is similar to that aspreviously discussed.

The turbine 104 of engine 101 is mechanically coupled to a gascompressor 114. A mechanical seal separates gas flow from the gascompressor 114 and the turbine 104 in a manner known in the art. The gascompressor 114 is in fluid communication with an inlet passageway whichis in fluid communication with either an oxygen supply or atmosphericair supply. In operation, air or oxygen is then drawn from therespective supply into the gas compressor 114 via rotation of compressorblades (not shown) driven by the turbine 104 by products of combustion(POC) driving the turbine blades. The gas compressor 114 is in fluidcommunication with a compressed gas passageway 116. The compressed gaspassageway 116 is in fluid communication with a plurality of sealedrecuperator units 120.

Specifically, the compressed gas passageway 116 is in fluidcommunication with a plurality of circumferentially spaced, sealedrecuperator unit inlets 118 of respective sealed recuperator units 120.Respective circumferential passageways P are defined between the secondrecuperator units 120. Each sealed recuperator unit 120 also includes asealed recuperator unit outlet 122 which is in fluid communication withthe sealed recuperator unit inlet 118. Each of the sealed recuperatorinlets 118 and sealed recuperator outlets 122 is defined by ellipticalor elongate lips 123 a and 123 b. The sealed recuperator unit outlets122 are in fluid communication with an annular shaped compressed gasplenum or an intermediate passageway 124, which functions as a frame,which is then in fluid communication with a compressed gas inlet to thecombustor 102. A portion of the passageway 124 circumferentiallysurrounds an outer surface of the combustor 102. Each of the sealedrecuperator units 120 is involute shaped and has the compressed airenter and leave the sealed recuperator units in radial directions R andR′. The gas then travels through the sealed recuperator unit 120 in anaxial direction A. The plurality of the sealed recuperator units 120 arepositioned circumferentially about the combustor 102. Each of therecuperator units 120 is curved or involute shaped.

A plurality of curved or involute shaped opened units 130, shown in FIG.11, are positioned between respective sealed recuperator units 120 inthe spaced passageways P. Each opened unit 130 is involute shaped andincludes a corrugated or serpentine body 132 defining elongatedpassageways 133 for the POC (products of combustion) as shown in FIG.11. The sealed recuperator units are shown in phantom in FIG. 11. Eachof the sealed recuperator units 120 is secured to the annular shapedplenum 124. As shown in FIG. 12, the annular shaped plenum 124 includesa plurality of slots or passages 136. The slots 136 are in fluidcommunication with the compressed gas passageway 116. The slots 136 alsoreceive respective sealed recuperator unit inlets 118. Similar slots 136are provided and in fluid communication with the recuperator unitoutlets 122. Specifically, the sealed recuperator lips 123 a and 123 bare welded to the plenum 124 within the respective slots 136. The sealedrecuperator units 120 are fixedly held in place to the plenum 124,preferably by welding. The sealed recuperator units 118 and the openedunits 130 are also held in place by a cylindrical and adjustable sleeve138. The cylindrical and adjustable sleeve 138 compresses outer edges ofthe sealed recuperator units 120 and the opened units 130 so as to holdthem in intimate contact with each other. The sleeves may be loosened ortightened through fastening members 139. The sleeve 138 may be removedfor repair and cleaning of the sealed recuperator units 120 and theopened units 130. The sealed recuperator units 120, the opened units130, the sleeve 138 and the plenum chamber 124 define a matrix M. Anannular S-shaped seal S is attached to the sleeve 138 and prevents POCto pass between the sleeve 138 and the exhaust manifold 164. The openedunits 130 are removably secured to the frame 124 by the sleeve 138. TheS-shaped seal S is positioned intermediate the ends of the sleeve 138.

Referring to FIGS. 13 and 14, each of the sealed recuperator units 120includes a first involute shaped section 140 having an embossment 142and a second involute shaped section 144. A corrugated or serpentine,involute shaped member 146 is received by the embossment 142. Member 146is a heat transfer member. The first section 140 and the second section144 define a body 147. Edges 148 of the first section 140 and secondsection 144 are bonded together by either welding or brazing so as toform the sealed unit 120 having four sides 150, 152, 154 and 156. Thesealed recuperator unit inlet 118 and sealed recuperator unit outlet 122are positioned on side 154. The corrugated member 146, known as a metalfin, is received within a flow chamber defined by inner surfaces ofsections 140 and 144 which provide a plurality of elongated passagewaysfor gas to flow from the inlet 118 to the outlet 122. The corrugatedmember has a plurality of apexes 157 that contact respective innersurfaces of the sections 140 and 144. Preferably, the apexes 157 areattached to the inner surfaces of sections 140 and 144 by brazing. Ascan be seen in FIGS. 13 and 14, the corrugated member 146 has a length158 that varies with respect to a width 160. This arrangement isprovided so that the areas positioned closest to the sealed recuperatorinlet 118 and sealed recuperator outlet 122 have the largest spacingbefore contacting the corrugated member 146. It has been found in thisarrangement an even flow of the compressed gas passes across thecorrugated member 146.

A method to manufacture the sealed recuperator units 120 is as follows.The first section 140 with the embossment 142 and the second section 144are provided. Initially, these sections are relatively flat. Thecorrugated member 146 is coated with a brazing material and is placed inthe embossment 142. The second section 144 is placed over the firstsection 140. A plurality of these arrangements are stacked andsandwiched between graphite forms. The forms are weighted and the wholearrangement is placed in a furnace for a period of time. The wholearrangement is removed. This heating causes respective corrugatedmembers 146 to be brazed or welded at their apexes to adjacent innersurfaces of the first section 140 and second section 144. Further, thiscauses the first section 140, second section 144 and the corrugatedmember 146 to have an involute or curved shape. Next, sides 150, 152 and156 of respective first sections 140 and second sections 144 are weldedtogether. Then, a U-shaped cross-sectional front member 161, whichincludes the inlet 118 and outlet 120; is slid over an end of theunwelded sides of the sections 140 and 144. Sides of the front member161 are welded or brazed to the respective sections 140 and 144, therebyforming the inlet 118 and the outlet 122 in the sealed recuperator units120. The sealed recuperator units include a body B having an innersurface 163 and an outer surface 165. A flow chamber F is defined by theinner surfaces 163.

Compressed gas or air, which is cooler than the POC, enters the sealedrecuperator unit 120 in directions which are transverse and different tothe direction of flow through the corrugated member 146. Specifically,the compressed air enters and exits the sealed recuperator unit in thesubstantially radial direction R and R′ and passes through thecorrugated member 146 in an axial direction A. The products ofcombustion pass through the opened units 130 in a substantially axialdirection A′ opposite to the flow of the compressed air as previouslydescribed. Directions A and A′ are transverse to directions R and R′.

The embodiment shown in FIGS. 10 a-14 overcomes several problems of theembodiment previously shown in FIGS. 1-9. First, the sealed recuperatorunits 120 can be made individually and individually quality tested. Inthis manner, leaks and other defects can be detected prior to assembly.Further, the complete assembled sealed recuperator units 120 are weldedor brazed to the plenum 124 and can be tested to determine whether anyof the sealed recuperator units 120 or their attachments leak. After theopen units 130 are positioned removably between the sealed recuperatorunits and the sleeve 138 is tightened, this compresses in intimatecontact the respective surfaces of the involute corrugated or serpentinebodies 132 against the respective outer surfaces of the involute shapedsealed recuperator units 120. Should any of the sealed recuperator units120 or the attachments leak, they can be repaired by partial disassemblyand replacement.

In operation, the compressed gas is completely separated from theproducts of combustion (POC) until the compressed gas enters thecombustion chamber. Further, over time, the recuperator 100 can becleaned by removing or loosening the sleeve 138 and removing therespective opened units 130. The opened units 130, which can becomefouled by becoming clogged with carbon and other products of combustion,can then be cleaned by washing or replacing with different cleaned ornew opened units 130.

Further, it has been found that a mechanical seal 128 can be provided toform a sealed passageway between the combustor 102 and the respectivecompressed gas passageway 116 and the heated compressed gas passageway124. Another advantage of the present invention is that the combustor102 is surrounded by either heated compressed or compressed gas sincethe plenum 124 circumferentially surrounds an outer surface of thecombustor, thereby eliminating the necessity of providing insulatingmaterial around the exterior of the combustor housing. Hence, inoperation, fuel is ignited in the combustor 102. The product ofcombustion (POC) then flows from the combustor 102 and drives theturbine 104, which drives the compressor 114 and an electric generator(not shown), resulting in an energy system. The POC then flows throughthe exhaust passageway and into the exhaust gas inlet plane 108. The POCpasses through the corrugated bodies 132 of open units 130 in an axialdirection A′ as well as across outer surfaces of the sealed recuperatorunits 120. The POC exits the exhaust gas outlet plane 110 and into theatmosphere through the exit 112. Simultaneously, the compressor 114draws in gas (either intake air or oxygen) and compresses the air. Thecompressed air passes through the compressed gas passageway 116 intorespective sealed recuperator unit inlets 118 in a radial direction R.The compressed gas then flows through the corrugated members 146 in anaxial direction A and contacts inner surfaces of the first section 140and second section 144 of the sealed recuperator units 120. Direction Ais opposite to direction A′. The compressed gas exits the sealedrecuperator units 120 through sealed recuperator unit outlets 122 in adirection R′. The compressed gas then passes through the plenum 124 andenters the combustor 102 to be ignited with fuel to form POC. The POCpasses heat to the compressed gas through a reverse flow directionthrough the sealed recuperator units 120 and the open units 130. Therespective units 120 and 130 do not permit mixing of compressed gas andPOC at the point of heat transfer 147. Heat transfer takes place betweenthe POC and the compressed air or oxygen through the sealed body B ofthe sealed recuperator units 120. As also can be seen, the matrixassembly M, which is defined by the units 120 and 130 and the sleeve138, is received within a volume or recuperator chamber 162 defined bythe two piece, annular shaped exhaust manifold or enclosure 164 as shownin FIG. 10.

Another aspect of the present invention is the ability to repair therecuperator 100. Specifically, the recuperator 100 may be easilyseparated from the turbine 104 and the combustor 102. This isaccomplished through the use of a combustor housing 200 and a frontplate 202. The front plate 202 is secured to the combustor 102. Thefront plate 202 is threadably, removably secured to the combustorhousing 200 through fasteners 204.

Referring to FIGS. 15-19, the combustor housing 200 is made of stainlesssteel and includes a plurality of spaced passageways 206 to partiallydefine the compressed gas passageway 116. The combustor housing 200surrounds the combustor 102. Solid sections 208 are defined adjacent thespaced passageways 206. Fuel nozzle receipt holes 210 are defined withinthe solid sections 208. Also, locating pin holes 212 are defined in thesolid sections 208. The front plate 202 is mechanically secured to theturbine 104 and the combustor 102. Fluid seals 214 are provided adjacentopposite ends of a portion of the combustor housing 200 so thatcompressed air is separated in the compressed gas passageways 116 fromthe plenum 124. To gain access to the recuperator 100, the fastener 204is removed and the front plate 202 is moved in an axial direction alongwith the combustor 102 (which is secured to the front plate 202) untilit is clear of the turbine. Locating pins 205 are then removed from pinholes 212 to remove the combustor 102. The matrix M may be removed byremoving fastener 221, fastener 218 and the rear shell 220. As can beseen, this arrangement enables easy repair of the combustor 102 or thematrix M.

In some instances the fuel used may be a liquid fuel, such as dieselfuel. Should an igniter fail, then the combustor and other areas,particularly the plenum 124, may have liquid fuel resting in a lowestpoint of the plenum chamber 124. This could result in problems. Toremove this liquid fuel, a purge system 300 is provided, as shown inFIG. 10 a. The purge system 300 includes a perforated tube or conduit302 positioned in a lowest portion of the plenum chamber 124. The purgetube 302 extends from the recuperator 100 and is connected to a solenoid306. In operation, when it is determined that liquid fuel may be pooledin the plenum chamber 124, then the compressed air passes through thecompressed gas passageways 116 and then into the plenum chamber 124. Thesolenoid 306 is opened and a small portion of the compressed air, whichis pressurized, and diesel fuel in the plenum chamber is pushed into thetube 302 through the perforations. The diesel fuel then exits the tube302 and travels to a non-perforated conduit 307 that is external of therecuperator chamber. The tube 302 has an exit pressure at atmosphericpressure. After a period of time or after no more liquid fuel is exitingthe tube 302, then the solenoid 306 is closed and no more compressed airpasses through the tube 302. Then the fuel can be introduced into thecombustor 102 and ignited.

Another aspect of the invention is attachment of the lips 123 b ofoutlet 122 of the sealed recuperator units 120 to the slots 136 of theplenum chamber 124. Referring to FIG. 20, initially each outlet lip 123b is positioned in a respective slot 136. It is important to note thatthe length L′ of the lip 123 b is such that a portion 400 of a tip Textends beyond the slot 136. It is important to note that the thicknessof the metal used in the lip 123 b is less than the thickness of themetal used in the plenum chamber 124. For example, the metal thicknessof the lip is 0.012 inch and the thickness of the plenum chamber is0.025 inch. Then the tip T of the lip 123 b is welded, for example,either by a torch or plasma arc welder to the adjacent portion of theplenum chamber 124 that defines the slot 136. This causes tip T to meltand bead and then sufficiently melt the area of the plenum 124 adjacentthe slot 136 to reach a liquid or melting state so that the tip T can bewelded to the plenum chamber 124, and after cooling forms a fluid tightwelded joint about the lip 123 b as shown in FIG. 21. Similarly, lip 123a is welded to the appropriate frame member in a similar manner asdescribed above for lip 123 b.

As can be seen in FIG. 20, slot 136 is defined by a lip 402.

Although the present invention has been described with reference topreferred embodiments, obvious modifications and alterations of theinvention may be made without departing from the spirit and scope of theinvention. The scope of the present invention is defined by the appendedclaims and equivalents thereto.

1. A method for manufacturing a sealed recuperator unit comprising thesteps of: (a) providing a first section having an embossment; (b)providing a second section; (c) placing a corrugated member in theembossment; (d) placing the second section over the first section; and(e) welding said first section to said second section thereby forming asealed recuperator unit.
 2. A method as set forth in claim 1, furthercomprising the steps of: (f) forming a fluid inlet in said sealedrecuperator unit; and (g) forming a fluid outlet in said sealedrecuperator unit.
 3. A method as set forth in claim 2, furthercomprising the step of: brazing said corrugated member to said firstsection and said second section.
 4. A method as set forth in claim 1,further comprising the step of: welding a front member having a fluidinlet and a fluid outlet to the first section and the second section. 5.A method as set forth in claim 1 further comprising the steps of:curving said first section; and curving said second section.